1. Field
The present disclosure relates to a video coding apparatus and a video coding method.
2. Description of the Related Art
A standardization activity of a next-generation video coding system called HEVC (High Efficiency Video Coding) is currently progressed by a cooperation of ITU-T and ISO/IEC. For example, the standardization activity is disclosed in an HEVC written standard (draft) (High Efficiency Video Coding (HEVC) text specification draft 10 (for FDIS & Last Call)).
In the conventional video coding standard of H.264, coding is performed by unit of macro block having a 16-by-16-pixel size. On the other hand, in the HEVC, the coding is performed by unit of not only the 16-by-16-pixel size but also a CU (Cording Unit) that is one of four kinds of sizes of a 64-by-64 pixel, a 32-by-32 pixel, a 16-by-16 pixel, and an 8-by-8 pixel as illustrated in FIG. 1. As illustrated in FIG. 1, various sizes can be selected as the size of a PU (Prediction Unit) used in the inter prediction in the CU.
In the video coding standard of H.264, a direct mode is adopted in the coding of a motion vector. In the direct mode of H.264, one motion vector of a current macro block is fixed from a spatially or temporally near macro block. On the other hand, in the HEVC, a merge mode is introduced in order to enhance coding efficiency rather than the direct mode. In the merge mode of the HEVC, a motion vector candidate list (hereinafter, referred to as a “merge candidate list”) including a maximum of five motion vector candidates as index information is produced from the PUs spatially or temporally near the current PU. The motion vector is selected from the merge candidate list, and an index (hereinafter, referred to as a “merge candidate index”) on the merge candidate list of the selected motion vectors is coded in each PU, thereby improving the coding efficiency.